The purpose of this project is to provide consultation on statistical and epidemiological methodology in the design, interpretation, and evaluation of clinical trials of diagnosis, treatment, and prevention of cancer, and other studies requiring this kind of expertise. For some studies the Section provides full statistical support, including development of detailed study plans, assistance in the design of appropriate study forms, supervision of randomization (for trials) and collection, processing, and editing of data, performance of interim analyses during the progress of the study, preparation of progress reports, final analysis of study data, and collaboration in the preparation of scientific papers. During the past year the Section has continued to collaborate extensively on the design and implementation of the Community Intervention Trial for Smoking Cessation; key activities during this year were the Evaluation Cohort survey and surveys of worksites, religious organizations, health care providers, and community cessation resources. The Section has continued to provide full statistical support for the randomized clinical trials of multimodality treatment conducted by the Brain Tumor Cooperative Group. Other important activities under this project include monitoring and analyzing results from the use of stored sera to evaluate new markers for breast cancer; collaborating on re-evaluation of issues in the design of clinical trials for AIDS and on the specific design of a randomized trial for simultaneous prophylaxis of multiple opportunistic infections; investigating the consumption of fruit and vegetables in the American diet; collaborating on a study of food purchasing behavior and consumer nutrition education, involving a supermarket-based intervention; and designing an evaluation, using a cluster randomized design, of the Physician Primary Care Nutrition Guide.